1. Field of the Invention
The present invention relates to a liquid carrier withdrawal apparatus for a liquid electrophotographic imaging system for withdrawing a liquid carrier by separating the liquid carrier from a developer liquid embedded on a photoreceptor for a liquid electrophotographic imaging system.
2. Description of the Related Art
In a liquid electrophotographic imaging system such as a printer or copier, adopting a liquid electrophotographic method, a mixed solution of a toner and a liquid carrier is used as the developer liquid for developing a latent image formed on a photoreceptor. As the liquid carrier, hydrocarbon solvents are widely used.
FIG. 1 is a schematic diagram showing important parts of the liquid electrophotographic imaging system.
The liquid electrophotographic imaging system shown in FIG. 1 includes a belt-type photoreceptor 2 driven by a driving roller 1. A latent image is formed on the surface of the photoreceptor 2 by latent image forming means (not shown), and the latent image is developed by a development device 3 using the toner contained in the developer liquid embedded on the latent image portion. After the latent image of the surface of the photoreceptor 2 is developed, a squeegee roller (not shown) incorporated in the development device 3 squeegees the liquid carrier from the developer liquid on the surface of the photoreceptor 2 to then separate the liquid carrier from the photoreceptor 2.
The remaining liquid carrier which is not separated by the squeegee roller is separated from the photoreceptor 2 by a drying roller of the liquid carrier withdrawal apparatus. The drying roller 4, as shown in FIG. 2, includes a core 42 rotatably supported on a shaft 41 fixed on a predetermined support body 9 incorporated in the liquid electrophotographic imaging system, a shielding member 43 coated on the outer surface of the core 42, and an absorbing member 44 coated on the outer surface of the shielding member 43. The shielding member 43 is formed of an oleophobic material so that the oily liquid carrier is prevented from being absorbed into its body. The absorbing member 44 is formed of an oleophilic material such as silicon or polyethylene so that the oily liquid carrier is easily absorbed into its body.
The drying roller 4 is passively rotated by the movement of the photoreceptor 2. When the drying roller 4 is rotated, the liquid carrier contained in the developer liquid embedded on the surface of the photoreceptor 2 is absorbed into the absorbing member 44 of the drying roller 4, thereby separating the liquid carrier from the photoreceptor 2. The liquid carrier absorbed into the absorbing member 44 is prevented from being diffused into the core 42 by the shielding member 43. The liquid carrier absorbed into the absorbing member 44 of the drying roller 4 is then heated by a heating roller 5 (see FIG. 1) and evaporated in a casing 6. The evaporated liquid carrier is exhausted from the casing 6 by a fan 7 together with the air present in the casing 6, and is then sent to a condenser (not shown). The liquid carrier sent to the condenser is liquefied therein prior to withdrawal. The withdrawn liquid carrier may be recycled or disused.
In the conventional liquid carrier withdrawal apparatus having the aforementioned configuration, since a liquid carrier on a photoreceptor is absorbed into only the surface layer of a drying roller, the absorbing capacity for absorbing the liquid carrier is small. Also, since the liquid carrier absorbed into the drying roller is evaporated at the surface of the drying roller by a heating roller, the evaporating efficiency is poor. Also, to prevent the evaporated liquid carrier from being spread into the outside environment, sealing means including a casing must separately be provided to seal the space around the drying roller and the heating roller, so that the overall structure of the imaging system becomes complex. Also, the sealing means causes considerably cumbersome work in repairing or replacing a part such as the drying roller or heating roller. Also, to condense the liquid carrier exhausted from the casing, the liquid carrier and a considerable amount of air exhausted from the casing together with the liquid carrier must be condensed. Thus, the efficiency of the liquid carrier withdrawal apparatus is poor.